When producing beverage containers in a blow molding process, the so called preforms are first heated to an adequate temperature. The preforms are then fixed in blow molds and transformed into the desired container shape by controlled injection of air. Only when they have the desired container shape, they have the necessary volume to be filled with liquid. The containers usually have to be sterilized before filling to guarantee a long shelf life of the bottled liquid. With sufficient sterilization the addition of preservatives in beverages can be reduced.
Methods have been developed whereby the preforms are sterilized after tempering and before blow molding. These methods have been developed due to increasingly higher demands on the cleanness of the containers and due to the desired minimization of preservatives in beverages. Thereby a largely sterile process up to filling can be achieved and maintained.
EP 1 056 481 B1 describes a method for sterilizing hollow bodies, whereby a vaporized sterilizing medium is applied on the surfaces to be sterilized. The evaporation of the sterilizing agent is done outside the hollow body close to its opening. The sterilizing agent is introduced to and aspired from the inside of the hollow body, thereby generating a gas stream that distributes the agent to all surface areas. The hollow body can either be already in the shape of a beverage container or it can be a preform which is then blow molded into a beverage container.
JP 04 04 49 02 A describes a method for the sterilization of preforms before they are tempered and blow molded into the desired shape of a beverage container.
It has been customary to heat the preforms to the required temperature for blow molding by means of hot air and/or by infrared radiation. From WO 2007/131701 A2 a heating device for plastic preforms is known that uses microwave radiation.